Benefits of Increasing Grazing Height On Weed Suppression in Management-Intensive Rotational Grazing Systems in Wisconsin.

Prevention of weed establishment is a key benefit of management-intensive rotationally grazed pastures compared to other agronomic crops in Wisconsin.  However, weeds can still infest these fields leading to negative economic and animal health affects. In situations where herbicides cannot be used or when there is a significant legume component to the pasture, graziers have limited management options preventing the emergence and establishment of weeds.  Common weeds in Wisconsin pastures begin to germinate in late March to early April, providing an opportunity to prevent weed emergence. Experiments established in 2008 determined increasing grazing heights from fall through summer reduced emergence and establishment of burdock (Arctium minus) seedlings and spring intercepted photosynthetic active radiation was negatively correlated with burdock seedling density.  However, increasing residual height to reduce establishment of burdock reduced forage biomass from 25-37% compared to typical management.

In September of 2009 treatments were redesigned utilizing input from a focus group meeting consisting of local producers and stakeholders.  These treatments were implemented in November of 2009 and will continue through summer of 2010.  The new treatments are meant to reconcile results from 2009 grazing season with producer concerns over more practical implementation and variation of grazing intensities experienced throughout a growing season.  In addition, 2 sites have been established that use livestock (both beef and dairy) to implement a subset of grazing treatments.

Preliminary results suggest that increasing grazing heights to 8 inches in the fall will reduce germination of all weed species studied by 50-75%, and that maintenance of residual height is critical before the first grazing period in spring.

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See more from this Division: C06 Forage and Grazinglands
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